This invention is related to microwave integrated circuit (MMIC) packages, capable of surface mounting.
According to prior art, microwave IC packages can be classified into the following types:
1. Can-type Package
This type of structure is shown in FIG. 1. The bottom surface provides input and output pins and ground connection. A can covers the bottom seat. Signals are transmitted through these pins, which are wire bonded at the top to the input and output terminals of an integrated circuit (IC). Such a structure does not have surface mounting capability, and cannot operate at very high frequency. However, the cost of this kind of package is low, and is therefore quite popular.
2. Ceramic-brazing-type Package
This kind of structure is shown in FIG. 2 and disclosed in U.S. Pat. No. 4,901,041. A ceramic substrate is treated with thin-film process, and then precision-brazing at high temperature to yield the final structure. This structure has the advantage that it can be surface-mounted and has good high frequency performance up to 20 GHz due to small impedance mismatch of the interconnections. However, the package requires much more complex process such as high temperature brazing, and the cost is high.
3. Mechanical Type Package
This structure is shown in FIG. 3 and disclosed in U.S. Pat. No. 4,951,014. A machined holder provides all the input and output terminals and the ground plane. A circuit boards are placed inside the holder and interconnected with bond-wires. The integrated circuits are placed at the bottom of the holder or on the circuit boards, and connected to the input and output terminals. This type of package is primitive costly and cannot be surface mounted. The frequency response is not high due to mismatch error of the bond-wires.
Although the foregoing structures have different features, they all have a common characteristic, namely: the packages have only signal transmission capacity but not signal processing capability.